As given by the question
there are given that the function:
[tex]\begin{gathered} f(x)=\sqrt[]{6x} \\ g(x)=\sqrt[]{24x} \end{gathered}[/tex]Now,
To find the value of (f.g)(x), multiply the function f(x) with g(x)
Then,
[tex]\begin{gathered} f(x)\times g(x)=\sqrt[]{6x}\times\sqrt[]{24x} \\ =\sqrt[]{6x}\times2\sqrt[]{6x} \\ =2\times6x \\ =12x \end{gathered}[/tex]Hence, the correct option is A.